1. Field of the Invention
The present invention relates to an apparatus for removing impurities in liquid, wherein the impurities, volatile substances or the like in the liquid are subjected to gas-liquid contact with a gas phase so that they are transferred to the gas phase to separate or purify the liquid phase. Specifically, the present invention relates to an apparatus for removing impurities in liquid, which can be used under a compressed, decompressed, heated or cooled condition and is suitable for the following: purification of a liquid phase or recovery of a volatile substance wherein the volatile substance that is a halogenated organic compound such as trichloroethylene, methylene chloride or trihalomethane in the liquid phase is subjected to gas-liquid contact with a gas phase to emit the volatile substance in the liquid phase into the gas phase; purification of a liquid phase wherein a dissolved gas such as O2 or NH3 in the liquid phase is exposed to a gas phase such as N2, air, water vapor, He or Ar; separation or purification wherein an insoluble substance in a liquid phase is distilled out by steam distillation; or hydro-refining wherein sulfur contained in fuel or the like is subjected to gas-liquid contact with hydrogen gas to carry out desulfurization.
2. Description of the Related Art
Hitherto, as an apparatus for removing impurities in liquid, there has been known a plate tower (tray tower) type apparatus having therein porous plates, or a packed tower type apparatus wherein a filling material is regularly or irregularly filled.
However, in the packed tower type apparatus wherein a filling substance is regularly filled, a gas-liquid contact manner as using wet walls is carried out. Thus, used liquid is a little so that the liquid film on the surface of the filling substance becomes thin. Therefore, the efficiency of the gas-liquid contact is superior. However, if the load of the liquid gets large, the liquid film becomes thick so that the efficiency of the gas-liquid contact deteriorates. For this reason, a problem arises that the capacity of the liquid to be treated cannot be made large.
In the tray tower type apparatus, an effective area on the trays becomes small by a downcomer for conducting liquid on the surface of porous plates, so that a dead space is generated. Thus, troubles are caused by stay of liquid or adhesion or growth of solid or solid matters. Therefore, maintenance is necessary. Pressure loss is also large because the effective area on the trays gets less. For this reason, the pressure in the tower becomes high so that the following problems arise: power consumption and steam consumption increase and the yield of products also deteriorates. Furthermore, in order to prevent the generation of flooding, it is necessary that the flow rate of gas in the tower is set up to 1 m/second or less. Thus, the diameter of the tower increases. In order to adjust the flow of the gas and the liquid, a distributor is also necessary inside the tower.
An object of the present invention is to provide an apparatus for removing impurities in liquid, making it possible to improve its performance by an improvement in the ratio of recovery, save energy and space, make maintenance unnecessary, reduce pressure loss, make running management easy, and make a distributor unnecessary.
The apparatus for removing impurities in liquid according to the present invention comprises a static mixer arranged so that its longitudinal direction is vertical; a liquid supply mechanism supplying the liquid containing impurities from the upper end of the static mixer into the static mixer; and a gas supply mechanism supplying gas from the lower end of the static mixer into the static mixer. The static mixer is fabricated so that one or more mixing elements comprising a passage tube through which fluid can pass and one or more spiral blades arranged inside the passage tube are, continuously or through one or more spacers, arranged in the longitudinal direction thereof and the liquid drops down inside the static mixer and the gas rises up inside the static mixer, so that the two are subjected to gas-liquid contact inside the static mixer.
In the present invention, the liquid drops down inside the static mixer and the gas rises up inside the static mixer, so that the two are subjected to gas-liquid contact inside the static mixer. Thus, the impurities contained in the liquid are subjected to mass transfer to the side of the gas so that the impurities can be separated from the liquid or the liquid can be purified. For this reason, the purified liquid and the gas containing the impurities can be recovered or discharged.
In the present invention, fluid passes through the mixing element(s) wherein the spiral blades or blades are arranged, which is different from the tray tower manner in the prior art. Therefore, pressure loss can be reduced, and costs for motive power and consumption of water vapor can also be reduced. In addition, the liquid drops down and the gas rises up so that the efficiency of the gas-liquid contact increases. Thus, the efficiency for recovering the impurities is improved and the performance of the apparatus can be made high, so that energy can be saved.
The apparatus can be small-sized since pressure loss is low. Since the efficiency of the gas-liquid contact is also high, the impurities can be separated from the liquid or the liquid can be purified even if the ratio between the liquid and the gas is greatly changed. Therefore, maintenance of the apparatus becomes easy. Dead space is substantially lost so that maintenance is not required, since the efficiency of the gas-liquid contact is high.
In the present invention, the blade or blades are preferably arranged to be twisted in the right or left direction, and composed of one or more porous plates.
In this manner, the liquid and the gas can be uniformly dispersed in the whole of the mixing element(s). Therefore, the liquid can be more efficiently brought into contact with the gas in the static mixer. The upward and downward flows inside the passage tube are adjusted by means of the pores of the porous plate(s), so that no distributor becomes necessary. The fluid is uniformly dispersed so that the dead space can be more reduced. The thermal distribution of the fluid can also be made uniform.
The blade or blades are preferably missing in the center of the passage tube.
The flow rate (superficial velocity) of the gas in the static mixer is preferably from 1.0 to 10 m/second.
Since the diameter of the passage tube can be small, the whole of the apparatus can be made smaller.
The percentage of the area of pores in the porous plate or plates is preferably from 5 to 80%. The diameter of the pores in the porous plate or plates is preferably from 5 to 30 mm.
The impurities in the liquid is preferably brought in contact with the gas so that the impurities are gasified or reacted, whereby the impurities are separated from the liquid and discharged together with the gas.